This is a hard call to make since much of the question is psychological. What will make this group of people come on time, and what will cause it to disband? We cannot judge that without direct contact with the people. There are also pertinent factors that are not clear.
One question is how many people will find a minyan at a different time or place. This is only one factor. It is not against halacha to set a time for the minyan, even if it means that some will miss a minyan altogether. Just as you are not required to wait for a few stragglers after a minyan has arrived, you do not have to wait for ten stragglers. If people cannot “get their act together,” then they will have to make personal decisions as to where they will find a minyan. It is also possible, as you suggest, that by canceling the minyan a few times, you will actually enable more people to daven with a minyan more consistently.
Regarding the amount of time to expend getting to a minyan and waiting for its formation, it is apparently thirty-six minutes, not including the davening itself.[1] On the other hand, there are instances when a person simply cannot afford that much time, which brings us to our next point.
The most prominent variable to consider is whether the time that is wasted by waiting is people’s personal time or time that is “borrowed” from work. Certainly, halacha is very strict regarding not wasting an employer’s time. In the context of tefilla, the Shulchan Aruch[2] says that a hired worker should say a shortened Shemoneh Esrei if his employer does not want to extend his break. The Mishna Berura[3] adds that he cannot take out the extra time to daven with a minyan without his employer’s tacit permission. Thus, if the time waiting causes people to be missing for more time than they are allotted, it would be wrong to wait unless the time can be made up in a way that is acceptable to each person’s employer. One should be extra careful not to contribute to creating an impression that religious Jews have a tendency of disappearing from work for extended periods, which is a serious chillul HaShem.
If the waiting time is on free time, then there is more reason to try to be flexible and to be forgiving to stragglers, unless this is counterproductive. Perhaps, one could even think of some worthwhile, creative solutions. One would be to start group learning (of something which lends itself to starting and stopping on short notice), or at least have learning materials available. This way the waiting time can be productive, and, hopefully, it will encourage people to come earlier and/or be less agitated when waiting for stragglers.
If the situation warrants it, you could arrange matters such that if the minyan gets together on time, then you do a full chazarat hashatz, and if it is late, then you do a shortened one.[4] This is a little dangerous if the minyan’s longstanding minhag is to do the full one and it is phased out because of negligence. We cannot judge from here whether or not the situation warrants the risk.